diff --git a/lib/cartodb/server_options.js b/lib/cartodb/server_options.js
index 76447bc5..5c25c3f5 100644
--- a/lib/cartodb/server_options.js
+++ b/lib/cartodb/server_options.js
@@ -38,7 +38,8 @@ module.exports = function(){
         req.params.processXML = function(req, xml, callback) {
           if ( req.dbuser ) {
             // Only edit XML when authenticated
-            xml = xml.replace(/(<Parameter name="user"><!\[CDATA\[)[^\]]*(]]><\/Parameter>)/, "$1" + req.dbuser + "$2");
+            if ( ! me.rx_dbuser ) me.rx_dbuser = /(<Parameter name="user"><!\[CDATA\[)[^\]]*(]]><\/Parameter>)/;
+            xml = xml.replace(me.rx_dbuser, "$1" + req.dbuser + "$2");
           }
           callback(null, xml);
         }